Physiological stress detector device and system

ABSTRACT

A method, system and device for measurement of a blood constituent level, including a light source, a light detector proximate an organ surface, adjustable gain amplifiers, and a processor/controller connected within a processing unit operative to separate AC and DC signal components. The device may determine the level of blood constituent, may use this level for monitoring and/or to activate an alarm when the level falls outside a predetermined range, may be applied to monitoring conditions of apnea, respiratory stress, and reduced blood flow in organ regions, heart rate, jaundice, and blood flow velocity, and may be incorporated within a monitoring system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/390,169, filed Mar. 18, 2003, entitled “Physiological stress detectordevice and system,” which is a continuation-in-part application of U.S.patent application Ser. No. 09/147,683, filed Feb. 1, 2000, entitled“Physiological stress detector device and system,” both of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to instruments that operate on theprinciple of pulse oximetry, in particular, to non-invasive hemoglobinsaturation detectors and methods, and may be generally applied to otherelectro-optical methods of measuring blood constituents.

BACKGROUND OF THE INVENTION

Electro-optical measurement of blood characteristics has been found tobe useful in many areas of blood constituent diagnostics, such asglucose levels, oxygen saturation, hematocrit, billirubin and others.This method is advantageous in that it can be performed in anon-invasive fashion. In particular, much research has been done onoximetry, a way of measuring oxygen saturation in the blood, as an earlyindicator of respiratory distress.

Infants during the first year of life are susceptible to breathingdisturbances (apnea) and respiratory distress. Sudden Infant DeathSyndrome (SIDS) is a medical condition in which an infant entersrespiratory distress and stops breathing, leading to the death of theinfant. Although the cause and warning signs of SIDS are not clear, ithas been shown that early detection of respiratory distress can providethe time to administer the aid necessary to prevent death.

Many types of baby monitors are currently available, from simple motiondetectors to complicated systems which stream oxygen enriched air intothe infant's environment. Some of the more accepted monitoring methodsinclude chest motion monitors, carbon dioxide level monitors and heartrate (pulse) monitors. Unfortunately these methods often do not give theadvance warning necessary for the caregivers to administer aid. Inaddition, these monitors are administered by attaching a series ofstraps and cords, which are cumbersome to use and present astrangulation risk.

The chest motion monitor gives no warning when the breathing patternsbecome irregular or when hyperventilation is occurring, since the chestcontinues to move. Distress is only noted once the chest motion hasceased at which point there may only be a slight chance of resuscitationwithout brain damage. In addition these devices are known to have a highlevel of “false alarms” as they have no way to distinguish between thelapses in breathing which are normal for an infant (up to 20 seconds)and respiratory distress. These devices can cause excessive anxiety forthe caregivers or cause them to ignore a signal, which is true afterresponding repeatedly to false alarms.

Among other symptoms, SIDS causes an irregular heartbeat, resultingeventually in the cessation of heartbeat with the death of the infant.There are some instruments, which use the EKG principle to monitor thisclinical phenomenon. This is a limited method that has a very high rateof false positives since the monitors have inadequate algorithms todetermine what is a SIDS event. Obviously, this is not a convenientmethod, nor is it desirable to have the infant constantly hooked up toan EKG monitor.

In light of these disadvantages a better method to use is a form ofelectro-optical measurement, such as pulse oximetry, which is awell-developed art. This method uses the difference in the absorptionproperties of oxyhemoglobin and deoxyhemoglobin to measure blood oxygensaturation in arterial blood. The oximeter passes light, usually red andinfrared, through the body tissue and uses a photo detector to sense theabsorption of light by the tissue. By measuring oxygen levels in theblood, one is able to detect respiratory distress at its onset givingsufficiently early warning to allow aid to be administered as necessary.

Two types of pulse oximetry are known. Until now, the more commonly usedtype has been transmission oximetry in which two or more wavelengths oflight are transmitted through the tissue at a point where blood perfusesthe tissue (i.e. a finger or earlobe) and a photo detector senses theabsorption of light from the other side of the appendage. The lightsources and sensors are mounted in a clip that attaches to the appendageand delivers data by cable to a processor. These clips are uncomfortableto wear for extended periods of time, as they must be tight enough toexclude external light sources. Additionally, the tightness of the clipscan cause hematoma. Use of these clips is limited to the extremitieswhere the geometry of the appendages is such that they can accommodate aclip of this type. The clip must be designed specifically for oneappendage and cannot be used on a different one. Children are too activeto wear these clips and consequently the accuracy of the readingsuffers.

In another form of transmission oximetry, the light source and detectorare placed on a ribbon, often made of rubber, which is wrapped aroundthe appendage so that the source is on one side and the detector is onthe other. This is commonly used with children. In this method error ishigh because movement can cause the detector to become misaligned withthe light source.

It would be preferable to be able to use the other type of pulseoximetry known as reflective, or backscattering, oximetry, in which thelight sources and light detector are placed side by side on the sametissue surface. When the light sources and detector can be placed on thetissue surface without necessitating a clip they can be applied to largesurfaces such as the head, wrist or foot. In cases such as shock, whenthe blood is centralized away from the limbs, this is the way meaningfulresults can be obtained.

One difficulty in reflective oximetry is in adjusting the separationbetween the light source and the detector such that the desired variablesignal component (AC) received is strong, since it is in the alternatingcurrent that information is received. The challenge is to separate theshunted, or coupled, signal which is the direct current (DC) signalcomponent representing infiltration of external light from the AC signalbearing the desired information. This DC signal does not providepowerful information. If the DC signal component is not separatedcompletely, when the AC signal is amplified any remaining DC componentwill be amplified with it, corrupting the results. Separating out thesignal components is not a simple matter since the AC signal componentis only 0.1% to 1% of the total reflected light received by thedetector. Many complicated solutions to this problem have been proposed.

If the light source and detector are moved further apart, this reducesthe shunting problem (DC), however, it also weakens the already weak ACsignal component. If the light source and detector are moved closetogether to increase the signal, the shunting (DC) will overpower thedesired signal (AC).

Takatani et al., in U.S. Pat. No. 4,867,557, Hirao et al., in U.S. Pat.No. 5,057,695 and Mannheimer, in U.S. Pat. No. 5,524,617 all disclosereflective oximeters that require multiple emitters or detectors inorder to better calculate the signal.

A number of attempts have been made to filter out the DC electronically(see Mendelson et al., in U.S. Pat. No. 5,277,181). These methods arevery sensitive to changes in signal level. The AC remaining after thefiltering often contains a small portion of DC, which upon amplificationof the AC becomes amplified as well, resulting in inaccurate readings.Therefore, this method is only useful in cases where the signal isstrong and uniform.

Israeli patents 114082 and 114080 disclose a sensor designed to overcomethe shunting problem by using optical fibers to filter out the undesiredlight. This is a complicated and expensive solution to the problem thatrequires a high level of technical skill to produce. In addition, it isineffectual when the AC signal is relatively weak.

As can be seen from the above discussion, the prior art methods ofaddressing the AC/DC signal separation problem in reflective oximetrytechniques are complicated and expensive. Therefore, it would bedesirable to provide a simple, low cost and effective method forachieving accurate reflective or transmitted oximetry detection ofrespiratory stress.

SUMMARY OF THE INVENTION

Accordingly, it is the broad object of the present invention to overcomethe problems of separating the shunted light from the signal in order toprovide a physiological stress detector that achieves accurate readings.

A general object of this invention is to overcome the problems ofseparating the shunted light from the signal in order to provide arespiratory stress detector that achieves accurate pulse oximetryreadings for respiratory stress applications.

The present invention discloses a small, independent, sensor, forinvasive and non-invasive applications unencumbered by cables or wires,which is capable of being attached to different body parts, tocomfortably and accurately monitor blood constituent levels and thepulse of an infant or any other living organism. The apparatus may beapplied to any part of the body without prior calibration. Accuratereadings of blood constituent levels are obtained using the inventivemethod in which a precise separation of the AC and DC signal componentshas been achieved, allowing each signal component to be amplifiedseparately. In order to accomplish this precise separation, the signalcomponents are separated by a novel signal processing technique.

The inventive sensor may be adapted for many health-monitoringsituations including infant monitoring for SIDS, fetal monitoring, etc.

In an embodiment adapted for SIDS, the sensor is designed to applyreflective oximetry techniques, so as to comfortably and accuratelymonitor the arterial oxygen levels and the pulse of an infant or anyother living organism prone to respiratory distress. This monitor isequipped with a processor capable of determining the need for an alarmand capable of signaling a distress signal to further alert to a crisis.

In another embodiment, in addition to the alarm being generated from thesensor itself, readings will be radio-transmitted to a base station,possibly at a nurse's station, to allow monitoring of the reading, andanother alarm will be activated from the base station when the readingsare outside of the accepted range.

In another embodiment, the apparatus is mounted in a sock-type mountingsuch that the apparatus is properly applied when the sock is put on inthe usual fashion. In addition, the sock-type apparatus blocks entranceof external light to the area of the sensor apparatus.

In yet another embodiment, the apparatus is mounted on a ribbon-typemounting such that the apparatus is properly applied when the ribbon istied around the head or other body part. In addition, the width of theribbon is such that it will block entrance of external light to the areaof the sensor apparatus. Additionally, the ribbon may be of dark color,which also blocks entrance of external light to the area of the sensorapparatus.

In yet another embodiment, the apparatus is mounted on a bracelet-typemounting such that the apparatus is properly applied when the braceletis fastened to the wrist or other body part. In addition, the width ofthe bracelet is such that it blocks entrance of external light to thearea of the sensor apparatus. Additionally, the bracelet may be of darkcolor, which also blocks entrance of external light to the area of thesensor apparatus.

There is therefore provided, in accordance with a preferred embodimentof the present invention, a non-invasive device for measurement of bloodsaturation and heart pulse rate of an organ. The device includes ahousing unit having at least one light source, providing light directedtoward the surface of the organ, the light being reflected from theorgan, a sensor device spaced apart from the light source and beingsensitive to intensity levels of the reflected light for producingintensity signals in accordance therewith and a processing unit forprocessing the intensity signals received from the sensor device and forproducing output signals.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the device further includes a transmitter configuredto transmit the output signals to a receiver at a remote location. Thedevice may further include a display unit for displaying the outputsignals.

Additionally, there is also provided, in accordance with a preferredembodiment of the present invention, a monitoring system which includesa non-invasive device for measurement of blood saturation and heartpulse rate, and a receiver configured to indicate an alert when theblood saturation or heart pulse rate falls outside of a pre-determinedrange.

The non-invasive device may include a housing unit configured to fit awrist or ankle, including a baby. The housing unit includes at least onelight source, providing light directed toward the surface of the organ,the light being reflected from the organ, a sensor device spaced apartfrom the light source and being sensitive to intensity levels of thereflected light for producing intensity signals in accordance therewith,a processing unit for processing the intensity signals received from thesensor device and for producing output signals and a transmitterconfigured to transmit the output signals to a receiver at a remotelocation. The processing unit may be integrated with the sensor device.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the display unit may be configured in the shape of awatch. The display unit may include a memory storage unit for storingthe output signals. Furthermore, the transmitter may be integrated withthe display unit.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the device further includes an alerter configured totransmit an alert signal. The alerter may be configured to transmit asignal whenever the blood saturation or heart pulse rate falls outsideof a pre-determined range.

The alerter may also be configured to transmit data signals including atleast the blood saturation or heart pulse rate.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the housing unit may be configured to be attachableto a head covering, such as a cap, a hat and a bandanna, for example.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the housing unit may be configured to adhere to thesurface of the skin.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the housing unit may be configured to be integratedwithin a protective mask, including a search and rescue mask, gas mask,anti biological and chemical mask.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the device may further include a display orindication unit. The display or indication unit may include anindication of the well being of the wearer.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the receiving device at the remote location may be apersonal digital assistant (PDA).

Furthermore, in accordance with another preferred embodiment of thepresent invention, the housing unit may be configured to receive a humandigit such as a finger.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the housing unit may be configured in the shape of apen and the sensor device is located on the external face of the pen,thereby allowing the housing unit to be disposed proximate to the skin.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the processor develops a control signal when theadjustably-determined second gain amplification factor is established inthe second stage, the signal is measured and the control signal shutsoff the light source.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the control signal conserves energy by reducing theoperational duty cycle of the light source.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the first and second gain amplification factors aredetermined by the processor in an iterative process by adjustablysetting a gain amplification factor and measuring a dynamic voltagerange of the output signals to determine if the voltage range fallswithin a predetermined window established by the processor.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the light source comprises a single light-emittingunit capable of controllably providing light having a wavelength rangeselected from at least a first wavelength range and a second wavelengthrange. The first wavelength range is at least partially different fromthe second wavelength range. The single light-emitting unit can beswitched from emitting light within the first wavelength range toemitting light within the second wavelength range.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the light source includes at least a firstlight-emitting unit capable of controllably emitting light having afirst wavelength range and a second light-emitting unit capable ofcontrollably emitting light having a second wavelength range. The firstwavelength range is at least partially different from the secondwavelength range.

Furthermore, in accordance with another preferred embodiment of thepresent invention, the light source provides light having wavelengths inthe red and infrared ranges.

Other features and advantages of he invention will become apparent fromthe following drawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding, the invention will now be described, by wayof example only, with reference to the accompanying drawings in whichlike numerals designate like components throughout the application, andin which:

FIG. 1 is a schematic layout diagram of a physiological stress detectordevice, constructed and operated in accordance with the principles ofthe present invention;

FIG. 2 is an electronic schematic diagram of a prior art signalprocessing technique, for use with the device of FIG. 1;

FIGS. 3 a-3 b show, respectively, a prior art signal waveformrepresenting emitted and received light;

FIGS. 4 and 5 a-b show, respectively, arrangements for wearing thedevice of FIG. 1 on the body of an infant on a leg, foot or head;

FIG. 6 is an electronic block diagram showing the signal processingcomponents of the device of the present invention;

FIG. 7 is an algorithm of a signal processing technique performed inaccordance with the principles of the present invention;

FIGS. 8 a-b are, respectively, signal waveforms representing emitted redand infrared light used in the device of FIG. 1;

FIG. 9 is a timing diagram applied in an automatic gain adjustmentprocedure during signal processing;

FIG. 10 is a schematic illustration of a device for determining bloodflow velocity in accordance with another preferred embodiment of thepresent invention;

FIG. 11 is a schematic graph useful in understanding the method ofdetermining blood flow velocity used by the device of FIG. 10;

FIGS. 12 a-12 c are schematic illustrations of an exemplary applicationof a device for determining blood saturation and heart pulse rateaccording to an embodiment of the invention;

FIGS. 13 a-13 b are schematic illustrations of an exemplary applicationof a device for determining blood saturation and heart pulse rateaccording to another embodiment of the invention;

FIGS. 14 a-14 c are schematic illustrations of an exemplary applicationof a device for determining blood saturation and heart pulse rateaccording to another embodiment of the invention;

FIGS. 15 a-15 c are schematic illustrations of an exemplary applicationof a device for determining blood saturation and heart pulse rateaccording to another embodiment of the invention;

FIGS. 16 a-16 c are schematic illustrations of a monitoring systemaccording to an embodiment of the invention;

FIGS. 17 a-17 b are schematic illustrations of a monitoring systemaccording to another embodiment of the invention, and

FIGS. 18 a-18 c are schematic illustrations of an exemplary applicationof a device for determining blood saturation and heart pulse rateaccording to another embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following description presents a detailed construction of aphysiological stress detector device adapted for use in monitoringarterial oxygen levels. In this particular application, the reflectiveoximetry method uses light wavelengths in the red and infrared ranges,since these are most suitable for detecting oxygen saturation inhemoglobin. As will be understood by those skilled in the art,particular design features used for this application can be varied fordifferent applications. For example, in an application for monitoringjaundice through billirubin levels, other suitable, light wavelengthswould be used. Therefore, the light wavelengths discussed in thefollowing description are not intended to limit the scope of the presentinvention, and are to be understood as pertaining to the subject exampleonly.

Referring now to FIG. 1, there is shown a preferred embodiment of aphysiological stress detector device 10 constructed and operated inaccordance with the principles of the present invention. Device 10comprises a housing 12 arranged for placement in close proximity to askin surface 14. Housing 12 may be provided as a casing enclosing alight source 16 emitting two wavelengths, red and infrared, and a photodetector 18 spaced apart from the light source 16. Device 10 is designedto be operated such that when light source 16 emits light of a red orinfrared wavelength, the light penetrates skin tissue (arrow A) and aportion of the light is reflected back to light detector 18, along apath defined by line 20.

The light source 16 may be implemented as a single component, which cancontrollably emits red or infrared light. A non-limiting example of thelight source 16 is the selectable wavelength light emitting diode (LED)component model L122R6IR880, or for pediatric or prematurely born babyapplications the component model SML12R6IR880, both components arecommercially available from Ledtronics, CA, U.S.A. However, The lightsource 16 may also include two separate suitable light sources. Forexample, the light source 16 may include two separate light sources (notshown) such as an LED emitting red light and another different LEDemitting infrared light.

It is noted that, while, preferably, the light source 16 includes one ormore LEDs emitting in the suitable red and infrared ranges, other lightsources may be used such as incandescent lamps in combination withsuitable optical filters, various types of gas discharge or arc lamps,with or without optical filters, diode laser devices, or any other.

For the pulse-oximetry application the light detector 18 may be aphotodiode, such as the model BPW34 photodiode, or for pediatric andpremature born babies the model BPW34S photodiode, both commerciallyavailable from Siemens Semiconductor Group, Germany. However, many othertypes of photo-detecting devices may be used such as resistivephotocells, or any other type of photo detector, which has the requiredsensitivity at the wavelengths, used for the specific application of thedevice 10.

It is noted that the device 10 of FIG. 1 also includes furtherelectronic components (not shown in FIG. 1), which are disclosed indetail hereinbelow (as best seen in FIG. 6).

As described in the background of the invention, the device 10 employsnon-invasive reflective oximetry techniques to provide measurement ofblood characteristics useful in diagnostic procedures and detection ofphysiological stress. As mentioned, one difficulty in reflectiveoximetry is in adjusting the separation between light source 16 anddetector 18 such that the desired signal received by light detector 18is strong and not affected by shunted, or coupled, light from source 16.FIGS. 2 and 3 a-3 b illustrate this problem and the prior art techniquescurrently available for its solution.

In FIG. 2 there is shown an electronic schematic diagram of a signalprocessing filter 22 used to separate the variable signal (AC) componentof received light from the shunted (DC), or coupled, light. Theseparation is achieved by a blocking capacitor 24 on the input of anoperational amplifier 26 used to amplify the variable signal portion.The DC signal component of the received light, which does not passthrough blocking capacitor 24, forms the input of, and is amplified byoperational amplifier 28.

As illustrated in FIGS. 3 a-3 b, the signal waveform representing theemitted light, (FIG. 3 a) is substantially reproduced as a receivedsignal waveform (FIG. 3 b). Even after filtering by signal processingfilter 22, the AC signal component remaining ΔSIG is only a smallportion of a larger signal, which has been amplified by operationalamplifier 26, and therefore dominates the variable signal portion. Thus,this method of signal separation results in inaccurate readings ofreflected light, and cannot provide accurate information in oximetrymeasurements.

In FIGS. 4 and 5 a-b there are shown alternative configurations ofdevice 10, respectively, provided in a foot bracelet 30, a sock 32 wornaround the ankle, and a ribbon 34 worn around the head. In eacharrangement, casing 12 is designed to be held tightly against skinsurface 14 to reduce the amount of stray light entering into the opticalpath between light source 16 and detector 18.

Preferably, the casing 12 is made from a material opaque to light in therelevant spectral range to which the detector 18 is sensitive, such asan opaque plastic material, metal or the like. The foot bracelet 30, thesock 32 and the ribbon 34 may be made of a material, which allows thecasing 12 to be tightly pressed against the skin. This material may be aflexible material such as a flexible fabric. The material may also be aporous or woven material to prevent excessive perspiration of the skinthereunder.

Referring now to FIG. 6, there is shown an electronic schematic blockdiagram of device 10. Device 10 comprises a sensor 35 incorporatinglight source 16 and detector 18. The sensor 35 may also include apreamplifier circuit (not shown) for amplifying the output signals ofthe detector 18 and feeding the amplified signals to the processing unit40. It will be appreciated by those skilled in the art that the numbersof light sources and detectors can be varied while keeping the sameprocessing method. In addition, device 10 comprises a signal processingunit 40 including a pair of operational amplifiers A1 and A2, an analogto digital converter 42, a central processing unit (CPU)/controller 44,and a digital to analog converter 46. In critical applications, such asSIDS, when there exists a need for emergency first aid availability,when CPU 44 has determined that the value obtained is not within theacceptable range an output signal 47 is fed to an alarm unit 48 causingan alarm to be activated. Optional connections to an RF transmitter 50and PC computer 52 are available. Sensor 35 is designed to be powered bya small battery (not shown).

According to another embodiment of the present invention, processingunit 40 with or without alarm 48, RF transmitter 50 and/or PC 52 areconnected to the sensor 35 via a cable or by wireless transition. Inthis case sensor 35 does not require a battery.

It is noted that, the alarm unit 48 may activate a visual alarm, anaudio alarm, a tactile alarm (such as a vibratory signal), or anaudio-visual alarm. The alarm unit 48 may also initiate the automaticdialing of a telephone number and may also activate any combination ofany of the above types of alarms, or of other types of alarms.

The coupling of operational amplifiers A1 and A2 is between the outputof amplifier A1 and the input of amplifier A2. The gain amplificationfactor of each amplifier is set by the central processing unit 44 via asignal in accordance with an automatic adjustable gain techniquedescribed further herein. Analog to digital converter 42 provides adigital input signal 54 based on the level of output signal 56 fromamplifier A2. The central processing unit 44 is programmed to processthe information contained in input signal 54, and thereby determineblood oxygen saturation levels detected by sensor 35. The output signal47 from CPU 44 may be used to trigger alarm 48, or its information canbe transmitted by an RF transmitter 50 to a receiver 60 for remotestation processing. Data analysis can be performed by PC 52 based on adata output signal 53.

Based on the block diagram of FIG. 6, device 10 can be constructed inaccordance with state of the art electronic design techniques employing,for example a 8051 micro-controller, commercially available from IntelCorp, U.S.A., or any other suitable processor or controller to implementthe CPU/controller 44.

The properties of amplifiers A1 and A2 are selected in accordance withelectronic design rules well known in the art. In a non-limitingexample, amplifier A1 is the model PGA205AU programmable gaininstrumentation amplifier, and amplifier A2 is the model PGA204AUprogrammable gain instrumentation amplifier, commercially available fromBurr-Brown, AZ, U.S.A. However, the amplifiers A1 and A2 may be anyother suitable type of amplifier. For example, while in the preferredembodiment disclosed hereinabove each of the amplifiers A1 and A2 isshown as an operational amplifier unit, each of the amplifiers A1 and A2may be implemented as a multi-stage amplifier device containing morethan one amplification stages.

As mentioned in the background of the invention, problems with prior artreflective oximetry techniques are related to the measurement of the ACsignal component which forms a small part of the larger DC signalcomponent provided by light sensor 35. Whereas the previous techniquesinvolved use of a blocking capacitor 24 as described in FIGS. 2 and 3a-3 b, the present invention provides a novel solution to the signalamplification problem such that more accurate oximetry measurement maybe obtained.

It is noted that, depending on the specific detector used, the AC and DCsignal components generated by the detector 18 may be current or voltageAC and DC signal components, and that the terms AC signal component andDC signal component throughout the specification and claims define ACand DC components of the output signal of the detector 18 and mayinclude voltage signal components and current signal components.However, the AC and DC signal components may also include any other typeof electrical or photonic (optical) signal that may be the output of anysuitable detector type useful with the device of the present invention.

In accordance with the principles of the present invention, processingunit 40 applies a novel technique for separating the AC signal componentfrom the DC signal component. The steps carried out by CPU 44 in thistechnique are illustrated in the flow chart of FIG. 7.

In start block 62, CPU 44 begins its operation by initializing the gainof analog amplifiers A1 and A2 automatically. In block 64 the detectedsignal from sensor 35 is measured, and this is performed by providingoutput signal 56 from signal processing unit 40 to the analog to digitalconverter 42, so that it is converted to a digital input signal 54 forinput to CPU 44. In block 66, CPU 44 calculates the DC signal componentof the detected signal. A two-stage process achieves this.

In the first stage, output signal 56 is treated as a pure DC signal,such that CPU 44 takes the average of this signal level, and generates adigital output signal 67 which is converted by the digital to analogconverter 46 to an analog reference shift signal 68. In block 70,reference shift signal 68 is fed into the negative input of amplifier A1and amplifier A1 effectively neutralizes the DC component by applyingreference shift signal 68 against the detected signal from sensor 35.This produces a null output for input to amplifier A2.

In the second stage, in block 72, amplifier A2 receives the AC signalcomponent of the detected signal and amplifies it, thereby producing anoutput signal 56 containing information based on the reflective oximetrytechnique. This information, when converted to a digital signal inanalog to digital converter 42, provides digital input signal 54 to CPU44. In block 74, the oximetry calculation is performed by theCPU/controller 44 based on measurements derived from sensor 35, inaccordance with the information provided by digital input signal 54. Theresults of the oximetry calculation are provided as output signal 47 orin the form of a data signal 35 fed to a PC computer 52. Output signal47 may be used to activate an alarm 48 or it may be provided as thesignal for transmission via RF transmitter 50 to a remote receiver 60,to allow base station monitoring of the reading.

Referring now to FIGS. 8 a-b, there are shown respectively, pulse signalwaveforms representing light received in the red and infrared ranges bylight detector 18 in sensor 35. Light is provided by light source 16 inpulses each having, for example, duration of 1.6 milliseconds and aperiod of 15.6 milliseconds. The analysis of a typical light pulse isprovided in FIG. 9, showing the time scale division of the 1.6millisecond pulse into two cyclical gain adjustment periods 76 and 78,respectively. The red and infrared pulses are staggered so as tominimize interference between them.

In FIG. 9, a time division scale is developed in which each of thepulsed light waveforms is divided into two periods 76 and 78, eachhaving, for example, a maximum duration of 800 microseconds, duringwhich the gain amplification factor is set for each of operationalamplifiers A1 and A2. The first period is used to set the gain for andmeasure the DC signal component, and the second period is used to setthe gain for and measure the AC signal component.

The gain amplification factor is automatically adjusted in an iterativeprocess. After a predetermined delay, for example 50 microseconds, thegain amplification factor is set during interval 80, and the outputsignal 56 of signal processing unit 40 is measured to determine if itfalls within the window defined by CPU 44. For example, a dynamicvoltage range of between 0.4-4 volts is established by CPU 44, andoutput signal 56 is measured during interval 82, to see if it fallswithin this window. If it does, the gain amplification factor is fixedat its current value. If, on the other hand, output signal 56 does notfall within this window, another setting is provided by CPU 44 and againthe output signal 56 is measured. This process is repeated, in iterativefashion, within the first period of the cyclical gain adjustmentprocedure until the output signal 56 falls within the desired window.

If the desired window for the DC signal component is obtained before the800 microseconds of the first period has elapsed, the first period isshortened accordingly, and the second period is commenced, during whichthe same procedure is performed for the AC signal component. Once adesirable window is attained for the AC signal component, the secondperiod may be shortened accordingly, and CPU 44 sends a control signal84 to sensor 35, to shut off the light source for that pulse. In thisfashion, an energy savings is achieved by reducing the duty cycle oflight source 16, and reducing the current drain from the battery andextending its useful life. Control signal 84 is provided for eachindividual light pulse, so that the maximum energy savings is achieved.If the 800 microseconds have elapsed without establishing the gainamplification factor, the signal is ignored.

It is noted that, the values disclosed hereinabove for the pulseduration and pulse interval of FIGS. 8 a and 8 b and for the two periods76 and 78 of FIG. 9 are given as a non-limiting example only and may bereplaced by other suitable values depending, inter alia, on theavailable electronic component speed, the processing speed of theprocessor/controller 44 and the specific application type. For example,the pulse duration and pulse interval of FIGS. 8 a and 8 b can have thevalues of 0.6 milliseconds and 15.6 milliseconds, respectively, and thetwo periods 76 and 78 of FIG. 9 may each have the value of 300microseconds.

It is further noted that, while in the embodiment disclosed hereinabove(FIGS. 8 a, 8 b and 9) a DC gain correction procedure is performed foreach first time period 76 as disclosed in detail hereinabove, it wasfound that the DC correction can be performed much less often with nodeterioration of the devices performance and in some cases with aresulting improvement of measurement stability. For example, if atypical measurement cycle lasts approximately 4-5 seconds, in order toinclude a few heart pulse cycles, and includes 256 infrared and redlight measurement periods (each of the light measurement periodscomprising the time periods 76 and 78), performing the DC correctionprocedure only once for every 256 measurement periods (i.e. once foreach measurement cycle) results with a better stability. Thus, thenumber of times of performing the DC correction procedure of the presentinvention per measurement cycle may be varied for optimizing thestability and accuracy of the measurements. The optimal number of timesof performing the DC correction procedure of the present invention permeasurement cycle may depend, inter alia, on the optical parameters ofthe light source 16 and the detector 18 of the device 10 and on thespecific wavelengths implemented in the specific application.

An advantage of reducing the number of DC corrections per measurementcycle is that it reduces the computational load of the CPU 44, enablingincreasing the number of light measurement time periods within eachgiven measurement cycle or, alternatively, using a less powerful CPU 44to reduce the overall cost of the device 10 while conserving or evenimproving the accuracy and stability of the measurements.

The gain amplification factors are selected from a set of preselectedvalues. Amplifier A1, which acts to amplify the DC signal component, canhave gain amplification factors of 1, 2, 4 or 8. Amplifier A2, whichamplifies the AC signal component, operates in the amplification rangesof 1, 10, 100 or 1000.

An advantage of the ability to automatically switch between the gainamplification factors based on the iterative process performed by CPU44, is that it allows the device 10 to obtain oximetry measurements indifferent parts of the body without recalibrating the gain amplificationfactor for each area.

The separated AC and DC signals are calibrated using the formulas:

V _(AC)=(V _(a/d))K/(A _(AC) *A _(DC))

V _(DC)=(V _(a/d))K/(A _(AC) *A _(DC))

where V_(a/d) is the signal from the analog to digital converter andA_(AC) and A_(DC) represent the gain of the A2 and A1 amplifiers,respectively. Using these calibration equations it is possible tocalculate a value for each of the signal components (V_(AC) and V_(DC)),which is substantially separated from the other signal component.

Once the AC and DC signal components are calibrated, calculations forpurposes of determining oxygen saturation are performed by taking the ACand DC values for each wavelength and forming a ratio:

$G = \frac{{V({AC})}_{red}/{V({DC})}_{red}}{{V({AC})}_{infrared}/{V({DC})}_{infrared}}$

This ratio is used to calculate the oxygen saturation in the formula:

SatO ₂ =B−A*G

where B and A are constants. CPU 44 determines whether or not this valuefalls within the desired window, and in cases where the value isunacceptable and stress is detected, an output signal 47 is sent toalarm 48 and the alarm will turn on. Alternatively, or in addition, theoutput signal 47 can be sent to RF transmitter 50 for transmission toreceiver 60. Additional information, such as a log of all readings, maybe sent from CPU 44 as a data output signal 53 to PC 52.

In summary, the physiological stress detector device of the presentinvention provides a non-invasive method for more accurately measuringblood constituents in a compact, easily utilized design. It isespecially useful for application in SIDS monitoring systems due to itscompact lightweight design, which is provided with no cumbersome,dangerous cable connections.

An advantage of the devices and methods of the present invention is thatthe sensitivity and improved signal to noise ratio of the present methodenables use of transmitted methods of pulse oximetry under conditionswhere the signals are of low amplitude relative to the noises. In anon-limiting example, the method and devices may be particularly usefulfor transmitted oximetry under conditions of low blood perfusion such asin systemically shocked patients or in cases of severe hypothermia.

A major advantage of the present invention is in its application toreflective oximetry where the signals are usually of relatively lowamplitude. In particular, the sensitivity of the method and the devicesmay enable performing reflective pulse oximetry on regions of the body,which exhibit particularly low amplitude signals such as the wristregion, or the ankle region of adults and babies.

Reference is now made to FIG. 10, which is a schematic illustration of adevice 90 for determining blood flow velocity in accordance with anotherpreferred embodiment of the present invention.

The device 90 includes a housing 92 and two pulse oximetry devices 10 aand 10 b attached thereto. The devices 10 a and 10 b are constructed asthe device 10 disclosed hereinabove and are simultaneously operated toprovide an amplified pulse oximetry AC signal as disclosed in detail forthe device 10 hereinabove. The fixed distance D between the device 10 aand the device 10 b is represented by the double-headed arrow labeled D.The device 90 is placed on a region of skin A and the pulse oximetry ACsignal is simultaneously determined for each of the devices 10 a and 10b.

Reference is now made to FIG. 11, which is a schematic graph useful inunderstanding the method of determining blood flow velocity used by thedevice 90 of FIG. 10. The horizontal axis represents time and thevertical axis represents the amplitude of the reflective oximetry ACsignals. The curve 94A represents the AC signal output from the device10 a and the curve 94B represents the AC signal output from the device10 b. The minima 96A and 96B of the curves 94A and 94B, respectivelyrepresent the minima of the reflected AC signal due to the pulsation ofthe blood flow. The time delay ΔT between the reflection minima 96A and96B represent the time delay between the registration of a minimumreflectance by the device 10 a and its registration by the device 10 b.The delay results from the finite blood velocity and the distance Dseparating the devices. Since the distance D between the devices 10 aand 10 b is known, the approximate blood flow velocity V can bedetermined by calculating the value

V=D/ΔT.

The processing unit 40 of one of the devices 10 a or 10 b thus acquirestwo data sets. The first data set represents the AC signal component ofthe device 10 a and the second data set represents the AC signalcomponent of the device 10 b. Preferably, both of the data sets aredigital data sets and are sampled simultaneously. The data sets aresampled such that each data set includes at least one extremum datavalue corresponding to a minimum or a maximum value of the AC signalcomponent, the processing unit 40 detects the extremum point for each ofthe data sets using any method known in the art for detecting anextremum point. The processing unit then calculates the time interval ΔTbetween the corresponding extremum points of the first and the seconddata sets and calculates the blood flow velocity from the ratio ΔT/D.

Preferably, for devices using reflective pulse oximetry of the presentinvention, the extremum data values used are minimum values representingminimal values of reflected light due to maximal absorption of the lightfrom the light sources 16 of the devices 10 a and 10 b. However, theextremum values may also be maxima. For example, in an embodiment wheretransmitted pulse oximetry devices are used, the extremum values may bemaxima.

It is noted that, while each of the devices 10 a and 10 b may have a CPU44 as disclosed hereinabove, in accordance with another preferredembodiment of the present invention, the device 90 may include a singleCPU unit (not shown) which may be shared for performing all thecalculations and control functions disclosed hereinabove for theoperation of each of the devices 10 a and 10 b and for additionallyperforming the determination of ΔT and the calculation of theapproximate blood flow velocity therefrom.

It will be appreciated by those skilled in the art that suitable methodsfor detecting and timing the reflection minima 96A and 96B are wellknown in the art and are not included in the subject matter of thepresent invention, and will therefore not be described herein in detail.

It is noted that while the device and method for determining blood flowvelocity disclosed hereinabove is adapted for use with a pair of devices10 a and 10 b, a larger number of devices (not shown) may be usedtogether either as a multiplicity of device pairs or in any othergeometrical configuration for improving the accuracy of the measurementby averaging the results of multiple pair determinations or by any othersuitable computational method known in the art.

It is noted that, while the preferred embodiments of the presentinvention are particularly adapted for reflective pulse oximetryapplications, it may be also implemented in many other applications. Forexample, the method and the device of the present invention may beadapted to the monitor billirubin levels for the detection andmonitoring of jaundice, by suitably selecting a light source which emitswavelengths of light in the range selectively absorbed by billirubin,(approximately between 400-600 nanometer).

In another example, the present invention may also be used to detect andmonitor blood constituents, which have distinct absorbance peaks in thevisible, range, the near ultraviolet (UV) range or in both the visibleand the near UV range. For this type of applications one or more of thelight wavelengths used may be obtained from a gas discharge lamp or fromany another suitable source of light in the near UV range.

Another application of the present invention is the application of themethod for the determination and mapping of areas of organs suspected ofa reduced blood flow due to chronic or temporary clinical condition. Forexample if an internal or external organ is suspected to have developedgangrene the device 10 of the present invention may be used to map areashaving low or reduced blood flow by moving the device 10 along the organand in contact therewith and mapping areas of reduced blood flow byrecording and mapping the amplitude of the minima of the pulse oximetryAC component as disclosed hereinabove along the surface of the organ.This method may be particularly useful in mapping of such reduced flowareas in cases where regular transmitted pulse oximetry is notapplicable due to inaccessibility problems or due to very noisy signalconditions.

One exemplary application is mapping the external surface of theintestines using a small pre-sterilized reflective oximetry device suchas the device 10 of the present invention. In such a case transmittedoximetry devices cannot be used because it is not possible to position alight source and a light detector on opposite sides of the intestinalwall. The device 10 is particularly advantageous here because it can besimply moved along the external surface of the suspected intestinal partand because of its improved sensitivity and reduced noise level.

The above mapping method may be applied to many other organs such aslimbs suspected of blood flow disturbances due to a gangrene conditionor other diseases.

It is noted that the devices of the present invention may be implementedin a variety of different configurations. The devices 10 or 90 of FIGS.1 and 10, respectively may be connected to a computer (not shown) or amonitor (not shown). The computer or monitor may include a displaydevice (not shown).

An alternative configuration may include the device 10, connected to ahousing(not shown) wirelessly or by suitable wires. The housing may alsoinclude a liquid crystal display device (LCD), such as the LCD displaymodel G1216001N000-3D0E, commercially available from Seiko InstrumentsInc., Japan, suitably connected to the CPU 44 for displayingalphanumeric symbols representative of one ore more parameters of thepulse oximetry signal such as the pulse frequency, or amplitude or anyother data. The LCD display may also display the AC signal graphicallywith or without the alphanumeric data.

In a third configuration of the device of the present invention thepulse oximetry device includes all the optical and electronic componentswithin one single device shaped as a wristwatch like device to be wornas a self-contained unit. One non-limiting example (not shown) is adevice worn on the wrist and shaped like a wristwatch. All thecomponents of the device 10 are integrated within the device such thatthe light source 16 and the detector 18 are attached to the device so asto be in contact with the skin when the device is worn. All thenecessary electronic components disclosed hereinabove are alsointegrated in the device including a power source such as a battery. Thedevice may thus monitor signals, may or may not collect and store dataand may or may not activate an alarm unit or transmit a distress signalas disclosed hereinabove in detail. It is noted that this self containedintegrated device configuration may also be shaped to be placed incontact with the skin on the limbs, forehead or any other organ of thepatient by suitable means such as strips bands of flexible material,adhesives or any other suitable attachment means known in the art.

The self-contained integrated device configurations may be used for avariety of applications. For example, in a preferred embodiment of thepresent invention, the device may determine the pulse rate of thewearer. It is known that during a meal the pulse rate increases. Thepulse rate may thus be used for diet control by reporting to the userwhen the pulse rate reaches a predetermined value or when the increasein the pulse rate following the beginning of a meal is within apredetermined rate. The user may thus use the device for obtaining anindication of when to stop consuming food.

The device may also be used for radial pulse measurement in cardiacmeasurements and for various bio-feedback applications.

Reference is now made to FIGS. 12 a-12 c, which illustrate an exemplaryapplication of an oximetry device according to an embodiment of theinvention. Finger oximetry device, generally designated 100, may beconfigured for measuring blood saturation and heart pulse rate. FIG. 12a is an isometric top view of the device 100 and FIG. 12 b is asectional cut-away illustration of the device.

Device 100 comprises a housing 102 configured to receive a digit such asa finger. The housing 102 comprises a light source 104 (similar to lightsource 16 of FIG. 1) a detector 106 (similar to detector 18) and aprocessing unit 108.

The processing unit 108 is integrated with the detector 106 so thatprocessing of signals is carried out within the device 100. Device 100may also comprise a display unit 110 for displaying the output of theblood saturation and heart pulse rate measurements. The output maycomprise data and/or a graphic display such as a waveform, for example,

In an alternative embodiment, a disposable insert may be may be usedwithin the finger housing. In another alternative embodiment, the device100 may be linked by a cable to an external processing unit.

The device 100 may further comprise a transmitter (not shown) fortransmitting the output signals to a remote monitoring station 112, (anexample of which is shown in FIG. 12 c). The remote monitoring station112 may also include display unit 114. The remote monitoring station 112may be configured to activate an audio or visual alarm 116, for example,when the blood saturation or heart pulse rate falls outside of apre-determined range.

In an alternative embodiment, the device 100 may be utilized togetherwith a personal digital assistant (PDA), for example, which may beconfigured to receive the transmitted signals. The PDA would effectivelyact as the remote monitoring station.

Reference is now made to FIGS. 13 a and 13 b, which illustrate the frontand rear faces, respectively of an embodiment of the invention in theform of a stand-alone wireless device 120. Device 120 comprises a lightsource 122 and a detector 124. Light source 122 and detector 124 aresimilar to light source 16 and detector 18 of FIG. 1. A processor 126may be added.

Device 120 may also comprise a transmitter (not shown) for transmittingdata to a monitor such as PDA, for example, or any other receivingdevice thus allowing data to be transferred conveniently and speedily tothe physician's or the caregiver's PDA. The PDA thus converts a plainpulse-oximeter, for example, without display and accessories to acomplete measuring system. The PDA may also display the date inwaveform.

The device 120 may also have adhesive tape attached to its rear face sothat the device may be attached to a convenient part the skin.

In an alternative embodiment, the device, the device 120 may be wireddirectly to a PDA or any other receiving device.

Reference is now made to FIGS. 14 a-14 c, which illustrate an exemplaryapplication of the device according to an embodiment of the invention,generally designated 140, configured in the form of a pen. Device 140comprises a light source 142 and a detector 144. Light source 142 anddetector 144 are similar to light source 16 and detector 18 of FIG. 1.In addition, the pen device 140 may further comprise a display unit 146for displaying the output of the blood saturation and heart pulse ratemeasurements, for example.

The sensor comprising the detector 144 and light source 142 may belocated at the edge of the pen or at its side, for example. To obtain areading, the detector 144 is placed on the subject's skin such as theforehead. The readings may be displayed on the display unit therebyallowing the physician, nurse or any caregiver to speedily obtain anindication of the subject's blood saturation and heart pulse rate in amanner similar to obtaining a patient's temperature.

Reference is now made to FIGS. 15 a and 15 b, which illustrate anexemplary application of the device according to an embodiment of theinvention, generally designated 160, configured as a wristwatch.Wristwatch device 160 comprises a light source 162 and a detector 164located on the rear face of the watch. Light source 162 and detector 164are similar to light source 16 and detector 18 of FIG. 1. The wristwatch160 may further comprise a processing unit 166 and an alerter 168.

The wearer may summon help by pressing on the alerter 168, whichtransmits an alert to a receiving station, such as a PDA, for example.The watch device may also transmit data regarding the wearer's bloodsaturation and heart pulse rate for example, thus informing thecaregiver of the wearer's health state. Knowing the health state of thesender enables the physician or caregiver to determine the urgency ofthe situation and determine the appropriate action to take.

It will be appreciated by persons knowledgeable in the art that othervital signals, such as temperature , billirubin may be measured anddisplayed.

The processing unit 166 is integrated with the detector 164 so thatprocessing of signals is carried out within the device 160. A displayunit 169 may also be placed on the front face for displaying the outputof the blood saturation and heart pulse rate measurements.

In an alternative embodiment of the invention, the wrist watch 160 mayalso further comprise an alert device (not shown) activated in the eventthat either the blood saturation or heart pulse rate, for example, fallsoutside of a pre-determined range, to transmit data to a receivingstation such as a PDA.

In a further embodiment of the wristwatch device, shown in FIG. 15 c,the front face of the watch may be configured to include standard watchdisplay 170 such as time and date as well as indications of the bloodsaturation or heart pulse rate 172. This type of watch is useful forsportsmen, military personnel firemen and other active persons, forexample.

In a further embodiment of the wristwatch device, the faces of the watchmay be reversed so that the sensor device (light source 162, anddetector 164) is placed on the front face. The back face may be leftplain or contain the transmitter 166. The front face may be configuredto measure blood constituents from the wearer's finger, for example.

Reference is now made to FIGS. 16 a-16 c, which illustrate a monitoringsystem, generally designated 180. The monitoring system comprises abracelet 182 configured to fit a foot or arm and a base station 184.

The bracelet 182 comprises a light source 186 and a detector 188 locatedon the rear face of the bracelet. Light source 186 and detector 188 aresimilar to light source 16 and detector 18 of FIG. 1. The bracelet 182may further comprise a processing unit 190 and a transmitter (notshown). The processing unit 190 may be integrated with the detector 188.

The base station 184 is located at a remote location from the bracelet182 to receive the output signals from the bracelet in real timeindicating the blood saturation or heart pulse rate. The base station184 may be configured to activate an audio or visual alarm (for example)when the blood saturation or heart pulse rate falls outside of apre-determined range. Furthermore, the base station 184 may display thesignals received as data and/or in a waveform in addition as an alarm,

The monitoring system is wireless and is suitable for use with a youngbaby, for example, since there is not any danger to the baby from cablesbeing wrapped around the baby.

In an alternative application, a monitoring device 200, illustrated inFIGS. 17 a-17 b is illustrated. The monitoring device 200 may becombined with protective masks, such as search and rescue masks, gasmasks, and anti biological and chemical masks. The monitoring device 200comprises a tag having a display unit on its front face 204 and ameasuring device 206 comprising a light source 208 and a detector 210located on the rear face of device 200. Light source 208 and detector210 are similar to light source 16 and detector 18 of FIG. 1. The device200 may further comprise a processing unit 212 for processing the outputfrom the detector 210.

The rear face of the device 200 may be adhesive and may be placedproximate to the skin of the wearer to measure blood saturation andheart pulse rate. The front face of the device 200 comprises a displayunit 214, which may comprise green and red LEDs, to indicate well-beingand that help is needed, respectively. Alternatively, indicators, suchas the “√” and “X” could be used together with the green and red LEDs.

In an alternative embodiment, for example for persons wearing aprotective suitor mask, the display unit may be a separate unit incommunication with the sensor device containing the light source 208 anda detector 210, In this case, the sensor device would be placed on thebody of the wearer.

Reference is now made to FIGS. 18 a-18 c, which a further embodiment ofthe invention in the form of a tag device 220. Tag device 220 comprisesa light source 222 and a detector 224 on its rear face. Light source 222and detector 224 are similar to light source 16 and detector 18 of FIG.1.

Tag device 220 may also comprise a transmitter 226 for transmitting datato a PDA, for example, or any other receiving device thus allowing datato be transferred conveniently and speedily to the physician's orcaregiver's PDA. The PDA thus converts a plain pulse-oximeter, forexample, without display and accessories to a complete measuring system.

The tag device 220 may also have a “U” type spring clip 228 suitablyattached to the device. The clip 228 extends over the front face of thedevice. In use, the clip is suitably attached to a wearer's clothing,for example, so that the rear face of the device is placed proximate toa convenient part the skin for measuring of blood constituents.

In alternative embodiments, the tag device 220 may be fitted to theinside of a bandana, cap or hat so that the device is proximate thewearer's skin while also being hidden from view. It may also be fittedto a baby's diaper, for example. The tag device may also be configuredto measure/display other constituents such as temperature.

It will be appreciated by persons knowledgeable in the art, that thoughthe various applications described hereinabove with reference to FIGS.12-18 refer to the measurement of blood saturation and heart pulse rate,the applications are also applicable for the measurement of any bloodconstituent.

In all of the above applications of the self contained integrated deviceconfigurations, such as a bracelet-like device or the like the devicehas an advantage of being a compact, lightweight and convenient wearabledevice while still providing the high sensitivity, accuracy and relativeimmunity to movement artifacts of the present invention.

It is noted that the devices of the present invention, as used in thevarious applications disclosed herein above, may also be configured andused as monitoring devices in a hospital environment, as well as fordomestic use. It is further noted that the devices and methods of thepresent invention may be adapted for use of humans and animals.

Having described the invention with regard to certain specificembodiments thereof, it is to be understood that the description is notmeant as a limitation, since further modifications will now becomeapparent to those skilled in the art, and it is intended to cover suchmodifications as fall within the scope of the appended claims.

What is claimed is:
 1. A non-invasive device for measurement of bloodsaturation and heart pulse rate, comprising: a housing unit configuredto be worn as a wrist watch, said housing unit comprising: at least onelight source, providing light directed toward the surface of the skin incontact with the wrist watch, the light being reflected from said skin;a light detector spaced apart from said at least one light source andbeing sensitive to intensity levels of said reflected light forproducing intensity signals in accordance therewith; and a processingunit for processing said intensity signals received from said lightdetector for producing output signals, said processing unit comprising:first and second amplifiers for amplifying said intensity signals, eachin accordance with a respective first and second gain amplificationfactor; and a processor for automatically determining said first andsecond gain amplification factors in adjustable fashion; wherein duringa first stage, said first and second amplifiers amplify a DC signalcomponent of said intensity signals in accordance with predeterminedfirst and second gain amplification factors, said amplified DC signalcomponent being subtracted from said intensity signals at an input ofsaid first amplifier, to isolate an AC signal component of saidintensity signals, and wherein during a second stage, said secondamplifier amplifies said isolated AC signal component in accordance withsaid adjustably-determined second gain amplification factor, saidprocessing unit producing output signals in accordance with saidisolated AC signal component and said DC signal component andcalculating in accordance therewith, at least one blood constituentlevel.
 2. The device according to claim 1, wherein said processing unitcomprises mapping means for mapping the intensity of said AC signalcomponent along the surface of said skin to detect regions of said skinhaving a reduced blood flow.
 3. The device according to claim 1, furthercomprising a display or indication unit for indicating the well-being ofthe wearer.
 4. A non-invasive device for measurement of blood saturationand heart pulse rate, comprising: a housing unit configured to be wornas a wrist watch, said housing unit comprising: at least one lightsource, providing light directed toward the surface of the skin incontact with the wrist watch, the light being reflected from said skin;a light detector spaced apart from said at least one light source andbeing sensitive to intensity levels of said reflected light forproducing intensity signals in accordance therewith; and a processingunit for processing said intensity signals received from said lightdetector for producing output signals, wherein processing the intensitysignals is done through a signal analog path, said processing unitcomprising: first and second amplifiers for amplifying said intensitysignals, each in accordance with a respective first and second gainamplification factor; and a processor for automatically determining saidfirst and second gain amplification factors in adjustable fashion;wherein during a first stage, said first and second amplifiers amplify aDC signal component of said intensity signals in accordance withpredetermined first and second gain amplification factors, saidamplified DC signal component being subtracted from said intensitysignals at an input of said first amplifier, to isolate an AC signalcomponent of said intensity signals, and wherein during a second stage,said second amplifier amplifies said isolated AC signal component inaccordance with said adjustably-determined second gain amplificationfactor, said processing unit producing output signals in accordance withsaid isolated AC signal component and said DC signal component andcalculating in accordance therewith, at least one blood constituentlevel.
 5. A system comprising: a non-invasive device for measurement ofblood saturation and heart pulse rate, comprising: a housing unitconfigured to be worn as a wrist watch, said housing unit comprising: atleast one light source, providing light directed toward the surface ofthe skin in contact with the wrist watch, the light being reflected fromsaid skin; a light detector spaced apart from said at least one lightsource and being sensitive to intensity levels of said reflected lightfor producing intensity signals in accordance therewith; a processingunit for processing said intensity signals received from said lightdetector for producing output signals; and a transmitter configured totransmit said output signals to a receiver at a remote location; and areceiver configured to indicate an alert when the blood saturation orheart pulse rate falls outside of a pre-determined range; wherein saidprocessing unit comprises: first and second amplifiers for amplifyingsaid intensity signals, each in accordance with a respective first andsecond gain amplification factor; and a processor for automaticallydetermining said first and second gain amplification factors inadjustable fashion; wherein during a first stage, said first and secondamplifiers amplify a DC signal component of said intensity signals inaccordance with predetermined first and second gain amplificationfactors, and wherein the amplified DC signal component is converted by adigital to analog converter to an analog signal and is subtracted fromthe intensity signals, said amplified DC signal component beingsubtracted from said intensity signals at an input of said firstamplifier, to isolate an AC signal component of said intensity signals,and wherein during a second stage, said second amplifier amplifies saidisolated AC signal component in accordance with saidadjustably-determined second gain amplification factor, said processingunit producing output signals in accordance with said isolated AC signalcomponent and said DC signal component and calculating in accordancetherewith, at least one blood constituent level.
 6. The system accordingto claim 5, further comprising a display or indication unit forindicating the well-being of the wearer.
 7. A system comprising: anon-invasive device for measurement of blood saturation and heart pulserate, comprising: a housing unit configured to be worn as a wrist watch,said housing unit comprising: at least one light source, providing lightdirected toward the surface of the skin in contact with the wrist watch,the light being reflected from said skin; a light detector spaced apartfrom said at least one light source and being sensitive to intensitylevels of said reflected light for producing intensity signals inaccordance therewith; a processing unit for processing said intensitysignals received from said light detector through a signal analog paththereby producing output signals; and a transmitter configured totransmit said output signals to a receiver at a remote location; and areceiver configured to indicate an alert when the blood saturation orheart pulse rate falls outside of a pre-determined range; whereinprocessing the intensity signals is done through a signal analog path,said processing unit comprising: first and second amplifiers foramplifying said intensity signals, each in accordance with a respectivefirst and second gain amplification factor; and a processor forautomatically determining said first and second gain amplificationfactors in adjustable fashion; wherein during a first stage, said firstand second amplifiers amplify a DC signal component of said intensitysignals in accordance with predetermined first and second gainamplification factors, said amplified DC signal component beingsubtracted from said intensity signals at an input of said firstamplifier, to isolate an AC signal component of said intensity signals,and wherein during a second stage, said second amplifier amplifies saidisolated AC signal component in accordance with saidadjustably-determined second gain amplification factor, said processingunit producing output signals in accordance with said isolated AC signalcomponent and said DC signal component and calculating in accordancetherewith, at least one blood constituent level.
 8. A system comprising:a non-invasive device for measurement of blood saturation and heartpulse rate, comprising: a housing unit configured to be worn as a wristwatch, said housing unit comprising: at least one light source,providing light directed toward the surface of the skin in contact withthe wrist watch, the light being reflected from said skin; a lightdetector_spaced apart from said at least one light source and beingsensitive to intensity levels of said reflected light for producingintensity signals in accordance therewith, said light detector beingunaffected by shunted or coupled light from said light source; aprocessing unit for processing said intensity signals received from saidlight detector through a signal analog path thereby producing outputsignals; and a transmitter configured to transmit said output signals toa receiver at a remote location; and a receiver configured to indicatean alert when the blood saturation or heart pulse rate falls outside ofa pre-determined range; wherein said processing unit comprises: firstand second amplifiers for amplifying said intensity signals, each inaccordance with a respective first and second gain amplification factor;and a processor for automatically determining said first and second gainamplification factors in adjustable fashion; wherein during a firststage, said first and second amplifiers amplify a DC signal component ofsaid intensity signals in accordance with predetermined first and secondgain amplification factors, and wherein the amplified DC signalcomponent is converted by a digital to analog converter to an analogsignal and is subtracted from the intensity signals, said amplified DCsignal component being subtracted from said intensity signals at aninput of said first amplifier, to isolate an AC signal component of saidintensity signals, and wherein during a second stage, said secondamplifier amplifies said isolated AC signal component in accordance withsaid adjustably-determined second gain amplification factor, saidprocessing unit producing output signals in accordance with saidisolated AC signal component and said DC signal component andcalculating in accordance therewith, at least one blood constituentlevel.
 9. The system according to claim 8 wherein said processordevelops a control signal when said adjustably-determined second gainamplification factor is established in said second stage, said controlsignal is able to shut off said light source.
 10. The system accordingto claim 9 wherein said control signal conserves energy by reducing theoperational duty cycle of said at least one light source.
 11. The systemaccording to claim 8 wherein said first and second gain amplificationfactors are determined by said processor in an iterative process byadjustably setting a gain amplification factor and measuring a dynamicvoltage range of said output signals to determine if said voltage rangefalls within a predetermined window established by said processor.
 12. Anon-invasive device for measurement of blood saturation and heart pulserate, comprising: a housing unit configured to be worn as a wrist watch,said housing unit comprising: at least one light source, providing lightdirected toward the surface of the skin in contact with the wrist watch,the light being reflected from said skin; a light detector spaced apartfrom said at least one light source and being sensitive to intensitylevels of said reflected light for producing intensity signals inaccordance therewith, said light detector being unaffected by shunted orcoupled light from said light source; a processing unit for processingsaid intensity signals received from said light detector through asignal analog path thereby producing output signals; wherein processingthe intensity signals is done through a signal analog path, saidprocessing unit comprising: first and second amplifiers for amplifyingsaid intensity signals, each in accordance with a respective first andsecond gain amplification factor; and a processor for automaticallydetermining said first and second gain amplification factors inadjustable fashion; wherein during a first stage, said first and secondamplifiers amplify a DC signal component of said intensity signals inaccordance with predetermined first and second gain amplificationfactors, said amplified DC signal component being subtracted from saidintensity signals at an input of said first amplifier, to isolate an ACsignal component of said intensity signals, and wherein during a secondstage, said second amplifier amplifies said isolated AC signal componentin accordance with said adjustably-determined second gain amplificationfactor, said processing unit producing output signals in accordance withsaid isolated AC signal component and said DC signal component andcalculating in accordance therewith, at least one blood constituentlevel.
 13. The device according to claim 12 wherein said processordevelops a control signal when said adjustably-determined second gainamplification factor is established in said second stage, said controlsignal is able to shut off said light source.
 14. The device accordingto claim 13 wherein said control signal conserves energy by reducing theoperational duty cycle of said at least one light source.
 15. The deviceaccording to claim 12 wherein said first and second gain amplificationfactors are determined by said processor in an iterative process byadjustably setting a gain amplification factor and measuring a dynamicvoltage range of said output signals to determine if said voltage rangefalls within a predetermined window established by said processor. 16.The device according to claim 12, further comprising a display orindication unit for indicating the well-being of the wearer.
 17. Asystem comprising: a non-invasive device for measurement of bloodsaturation and heart pulse rate, comprising: a housing unit configuredto be worn as a wrist watch, said housing unit comprising: at least onelight source, providing light directed toward the surface of the skin incontact with the wrist watch, the light being reflected from said skin;a light detector_spaced apart from said at least one light source andbeing sensitive to intensity levels of said reflected light forproducing intensity signals in accordance therewith, said light detectorbeing unaffected by shunted or coupled light from said light source; aprocessing unit for processing said intensity signals received from saidlight detector through a signal analog path thereby producing outputsignals; and a transmitter configured to transmit said output signals toa receiver at a remote location; and a receiver configured to indicatean alert when the blood saturation or heart pulse rate falls outside ofa pre-determined range; wherein said processing unit comprises mappingmeans for mapping the intensity of said AC signal component along thesurface of said organ to detect regions of said organ having a reducedblood flow.